Ian Ridpath is a full-time writer, broadcaster and lecturer on astronomy. He is a Fellow of the Royal Astronomical Society and a member of the Association of British Science Writers. A former editor of Popular Astronomy, he is a regular contributor to Astronomy Now. Ian Ridpath's many books include Collins Guide to Stars and Planets, Gem Stars and The Monthly Sky Guide. He is also the editor of the highly respected Norton's Star Atlas - a must-have publication for most practical astronomers - and the Oxford Dictionary of Astronomy. Wil Tirion, who lives in the Netherlands, is the most highly regarded cartographer of celestial maps and charts in the world today.